A frequency scaling algorithm for high squint bistatic synthetic aperture radar

Since the two-dimensional spectrum of a point target cannot be obtained precisely by bistatic synthetic aperture radar (SAR), and the imaging results are not satisfied for high-squint-angle in front target observing, a new frequency scaling (FS) algorithm is proposed for high-squint-angle SAR based on the exact analytical bistatic spectrum. The method first transforms the echo into the two-dimensional frequency domain, and then chooses a frequency scaling function that is obtained based on an exact analytical spectrum to equalize the range migration of all points. Then, elimination of the residual video phase caused by the dechirp operation and inverse frequency scaling is performed to correct the second-order phase error. After range migration correction, the range-dependent second range compression term is eliminated using the nonlinear frequency scaling operation. The image is finally obtained by range and azimuth compression. Simulation results and comparisons with the normal FS algorithm show that ideal imaging can still be achieved even if the bistatic SAR system works at the equivalent high-squint-angle mode, and the main lobe and sidelobes of the impulse response of the point target can be well-resolved.